1. Field
The following description relates to a semiconductor device and a fabrication method thereof, and to, for example, a high voltage device or a lateral double diffused metal oxide semiconductor field effect transistor (LDMOS) that is implemented based on a fabrication process of a low voltage device for high performance logic and a fabrication method thereof.
2. Description of Related Art
During the fabrication process of display driver integrated circuits (ICs), nonvolatile memory devices such as flash memories, or audio codec devices having a speaker control logic embedded therein, a low voltage transistor and a high voltage transistor are commonly simultaneously implemented on the same substrate. The high voltage level required for respective semiconductor devices may be at least 10 V to several tens of voltages. On the other hand, the voltage level required for logic devices is being reduced to minimize the sizes of chips and to obtain high performance. Therefore, the difference between the high voltage required for the high voltage transistor components and the low voltage required for the low voltage components is continuing to increase. Thus, and it is difficult to fabricate the integrated circuits while forming two different types of transistors in the same substrate.
Technologies for forming a high voltage device or an LDMOS based on a logic process have been developed. These technologies allow the implementation of high voltage devices without additional processes. High voltage NMOS devices formed in this manner may includes a single gate oxide layer, a gate electrode, and a source/drain junction. The high voltage NMOS devices are fabricated using only processes used in logic processes. However, the performance of the high voltage components of these devices is not optimal.
For example, when a thick gate oxide layer is used in these devices as a gate oxide layer as in the logic processes, a high breakdown voltage (BVDss) characteristic is obtained but the current drivability is lowered and the on-resistance is increased. Further, when a thin gate oxide layer is used, the current drivability is improved, but the high breakdown voltage value is lowered.